While other public sectors can definitely have an impact on public safety, I don't believe there is the threat of violence or endangerment to the public that is so prevalent in policing.

Therefore I'm /less/ concerned about teachers, fire, post office, air traffic, etc. even though they have their issues.

There are many aspects of a union. Employees deserve a unified voice. What they don't deserve is to hold the system hostage with threats after they agree to work.